Technology and innovation aside, Hydro Flask does more than just keep beverages cold and drinkable for 24 hours. As anyone would tell you, Hydro Flasks, like other water bottles that came before them, (yes, we're talking to you, Nalgene) are social signifiers. 

"With Millennials, fitness and health are themselves signals," says NYU marketing professor Tülin Erdem (via The Atlantic). "They drink more water and carry it with them, so it's an item that becomes part of them and their self-expression." At their price points, Hydro Flasks are also seen as occupying a sweet spot for teens who want to be seen to be affluent enough to afford a pricey water bottle, but not showy enough to be flashing truly high-end branded items that their parents might be associated with. Why? Because they're teens and because such materialism is beneath them (via Eater).